Photoshop action help

How do I setup a photoshop action that only uses 'color range' on a certain shades of black. I'm having an issue where in my new photo studio with my new lighting setup I'm getting some strange lighting effect on the model's mid section. I'm not sure why and have for the time being given up on trying to work out why. So instead I've resorted to retouching it away.

In the image below. The left side is where you can see the strange lighting on the mid section and on the right side is where I've corrected it in photoshop. I'd like to just setup a photoshop action that will apply my adjustments only to the black section, and thus not change the model's skin color, or anything else not black. The photoshop action doesn't need to use 'color range' I just can't think of anything else that will grab black colors.

It's light hitting the suit. I'd use smaller lighting source modifier on models head and less on suit if light it's direct and or reflecting from background could also use black flags to block and absorb light - foam board maybe. Photoshop could use selective colour adjustment it's the bottom one when you click the half moon icon in adjustment panel choose black a use black slider. Don't know how well this would work in actions with different images.

I started with a smaller softbox above the model's head originally. I didn't quite like the results, or maybe I was doing it wrong. So I went to a medium size lightbox above the head. I'm now thinking about trying out a pretty large lightsource above the head to keep softening the fall off. I have a very large softbox somewhere, I just can't find it at the moment, but will test whenever I do find it.

I tried the selective color adjustment, couldn't figure out how to make it do what I want to do. So either I'm doing it wrong, or it is not possible. That is only make the correction to the black and not touch the model's skin via photoshop action.

Though if the big softbox does what I hope it will do, which is light more of the model's entire body and soften out the light fall off, then I might not need to worry about strange lighting on the model's body.

Excuse me for bringing this up, but I might have a solution for this problem. Althought this is an old thread and 4x6 might have already solve the issue, I hope this might be helpful to someone else in the future.

There is a simple way to affect only dark tones by using Blending options dialog box (Layer >> Layer style >> Blending options). Under "Blend if:Gray" area there are sliders with wich you can control the opacity of individual pixels based on the range of their tonal value. Using Alt key (Option on Mac, I guess) you divide the White slider and drag the handles to the left. It helps if you previously hide all other layers so you can see the checkerboard.

Here's a print screen so you can see what I mean.

This also works with Adjustment layers. For this image I would use Color balance with its Tone set to Shadows.

Hope this have been helpful. If you have any questions feel free to ask.